Balanced diaphragm for sound transmitters



July 29 1924. 1,503,011

D. A. SEALEY BAhANCED DIAPHRAGM FOR SOUND TRANSMITTERS Filed July 8, 1922 David AEEEL Patented July 29, 1924;

DAVID A. smart, on NEW YORK, n. Y.

BALANCED DIAPHRAGM FOR SOUND TRANSMITTERS.

Application filed July 8,

To all whom it may concern:

Be it known that I, DAVID A. SEALEY, a

at Newcitizen of the United States, residing York city, in the county of New York and State of New York, have inv'ented'certain new and useful Im rovements in Balanced Diaphragms for S hund Transmitters, of which the following is a specification, reference being had to the accompanying drawings.

This invention relates to sound transmit= ting apparatus, such as phonographs, telephone receivers, etc., and particularly to the diaphragm mountings therefor.

In the ordinary sound transmitting apparatus which uses a diaphragm, the diaphragm is clamped at its extreme margin between gaskets or other clamping devices and there is no balance to the pull or thrust 2 exerted at the center of the diaphragm.

The general object of my invention is to provide a diaphragm for transmitting or receiving apparatus wherein the diaphragm is not supported or clamped at its 2 extreme mar in but inward of the perimeter of the diaphragm, means being provided engaging the perimeter or engaging the diaphragm I beyond the annular fulcrum or clamping means which will balance the re- 39 sistance or stiffness of the diaphragm or balance the pull or force exerted at the center of the diaphragm.

My invention is illustrated in the accompanying drawing, wherein Figu i'e 1 is a section of a phonographicsoun 0x havin a diaphragm constructed in accordance wit my invention;

Figure 2- is a section of a telephone transmitter showing my improved diaphragm;

Figure 3 is a section of a wireless I'GCGllVBI showing my improved diaphragm;

F i re 4 is a fragmentary section of a telep one transmitter with springs instead of having a weighted perimeter;

5 Figure 5 is a face view of a diaphragm with a continuous weight around its perimeter;

. Figure dis a front view of a diaphragm with weights disposed at intervals around its perimeter. In Figure 1, I have illustrated the application of my, invention "to a phonograph diaphragm, and in this Figure 10 des1gnates 1922. Serial No. 573,613.

the ordinary sound box of a phonograph, whlch may be of any suitable construction, the construction not having anything to do with my invention, and 11 designates the diaphragm, which may be of mica, glass, steel, or any other suitable material and which may be in all respects precisely the same asan ordinary diaphragm. This dia-. phragm is supported inward of its perimeter by means of annular gaskets 12 shown as engaged with seats 13.

have illustrated the sound hour 16" as 65 being formed in two parts held in close engagement with each other by screws 14 whereby the gaskets may be clamped against the diaphragm, but it will be understood that this figure is purely diagrammatic and that the manner of construction of the sound box and the manner in which the gaskets are supported therein may be varied in many ways. The diaphragm 11 at its perimeter is shown as weighted by a weight or weights 15. I have illustrated a circular rod of lead or other suitable metal which has been cleft radially and forced upon the perimeter of the diaphragm and extends entirely therearound, but I do not wish to be limited to this, as any other suitable ma- 'terial may be used foi' this purpose and the weight need not extend entirely around the diaphragm. A number of weights may be used placed at spaced intervals, as illustrated in Figure 6. Furthermore, this Wei ht need not be ofmetal but might be ma e of a rubber strip attached to the perimeter of the disk. In all-cases, however, the member 15 which is attached to the perimeter of the diaphragm acts as a counterbalance to the thrust or force exerted at the center of the disk and preferably this I weight will extend equally on both faces of the diaphragm. 'The stylus arm 16 may be, of course, of any suitable character and has no bearingon my invention.

In Figure 2, I have illustrated the sound box of a telephone receiver or transmitter which, of course, includes the dia hra 11". mg supported etween gaskets'12" disposed inward of the perimeter of the diaphragm and the diaphragm is illustrated as being weighted at its extremity, as at, 15'. This weight, as before remarked, may extend en This diaphragm is illustrate as ceiver of a wireless telephone and the figure is typical of many other electro-magnetically operated receivers. In this case the sound box or casing of the receiver 18 carries within it an electro-magnet 19 acting on an armature 20, this armature being connected by a rod 21 to a disk or dia hragm 11 This diaphragm may be oi mica, glass or any other suitable material. Here again the diaphragm is supported inward of its perimeter by the opposed clamping gaskets 12 and the perimeter of the diaphragm is weighted, as at 15. This weight may extend entirely around the diaphragm or be disposed at intervals. Here again the figure is purely dia ammatic and is merely for the purpose of illustrating the fact that a weighted diaphragm may be used with a receiver of this type. In Figure 4, I have illustrated a diaphragm 11 which is supported by the gaskets 12, but the perimeter of the diaphragm-is counter-balanced not by a weight but b opposed springs 22.

It will be seen t at in all cases I balance the pull or thrust exerted. on the center of the diaphragm either by a stylus arm 16, by the electro-mag'netic traction, as in Figure 2, or by the pull of the rod 21, as illustrated in Figure 3, to thereby render the disk more flexible. I have found by experiment that a relatively heavy or stifi disk can be rendered quite flexible by the counterbalancing weights or springs. A counterbalanced disk permits a much easier move ment of the diaphragm and causes the diaphragm to respond much more readily to the movement of the needle on the record or to the fluctuation in the magnetic field than where the disk is not counter-balanced. My experiments have shown me that a diaphragm arranged as described produces louder tone and a tone of much better quality. I have found in actual experience that a metal diaphra m as used, for instance, in the ordinary te ephone transmitter or receiver is rendered very pliable and the slightest variations of the induced current in the magnet produces a corresponding movement in the diaphragm if the dia-s phragm is weighted or otherwise counterbalanced as described.

While. I do not wish to be limited to this, this invention is particularly applicable 150 the receivers and transmitters used with wireless telephones. Neither do T wish to be lirnited to the exact balancing of the diaphragm by the application to its perimeter of weights or sprlngs which will. exactly counter-balance the force exerted. at the center of the diaphragm, and it is within the purview of my invention for the weight on the perimeter of the diaphragm to be a little less or a little reater than is required to exactly balance the force at the center of the disk. 1' have found that in actual practice the diaphragm is rendered very flexible and vibrates much more easily and with much greater rapidity than where no weights are used upon the perimeter of the diaphragm but the diaphragm is clamped around its perimeter. The theory with regard to this action is as follows It will be seenthat the diaphragm is pivoted or fulcrumed on a circle 12. .There is a certain pull or thrust at the center of the diaphragm and if a portion of the diaphragm isconsidered as a lever pivoted at 13 and having a weight at its outer end and on the short arm of the lever and connected at its inner end to a thrustexerting member such as the stylus bar 16, then if the weight at the perimeter or end exactly balances this pull or thrust the center of gravity of the lever is at the fulcrum point and is exactly balanced about its point of support and this lever or section of the diaphragm oscillates at the end corres onding to the center of the diaphragm an at its perimeter or weighted end. If now the wei ht on the perimeter is a little less or a litt e greater t an required to exactly balance the force at the center ofthe disk, there is a condition which is analogous to that of a pendulum swinging on its fulcrum. It has been desired to clamp the diaphragm inward of its perimeter so as to per mit the better flexing of the diaphragm, but I havefound that this is not practical unless the weights or the springs 22 are used to more or less balance that portion of the diaphragm between the annular fulcrum and the center of the dia hragm where the thrust or force is exerted.

I claim 1. In a sound transmitting apparatus, a diaphragm, clamping means for the diaphragm rigidly engaging the opposite faces ofthe diaphragm inward of its periphery and disposed concentric to the center of the cent its perimeter for approximately cowl-- ter-balancing said force.

2. In a sound transmitting apparatus, a diaphragm, clamping means for the diaphragm rigidly engaging. the opposite face thereto to vibrate it, the perimeter of the of the diaphragm inward of its periphery diaphragm being weighted to a degree suf- 10 and disposed concentric to the center of the ficient to counterbalance the force applied diaphragm and constituting a fulcrum to the center of the diaphra m to vibrate it.

5 whereby the perimeter of the diaphragm In testimony whereof f hereunto aflix may flex as the diaphragm vibrates and, my signature. means located adjacent the center of the diaphragm whereby force may be applied DAVID A. SEALEY. 

